1. Field of the Invention
The invention relates to a waveguide, and in particular to an optical waveguide such as an optical fiber, the waveguide having a front face provided with a coating.
2. Description of Related Art
A waveguide such as an optical fiber may be intended to conduct light in the UV range, in the visible range and/or in the IR range. Waveguides usually have a front face through which the light emerges from the waveguide and/or enters the waveguide. The front face may be in contact with its environment at least at times and is therefore particularly prone to fouling. If the front end of the waveguide has been inserted in an insertion-type connector for light guides, the front face may also be subject to mechanical loads due to insertion processes, in which case the front face often has to withstand several hundreds to thousands of insertion cycles while it is in use.
Fouling or damage to the front face may result in a decrease in its permeability to light and hence in a degradation of the transmission properties of the waveguide as a whole. In extreme cases the waveguide becomes unusable when there is fouling to its front face.
It is already known for front faces of waveguides to be provided with coatings such as anti-reflection coatings (AR coatings) in order to increase the passage of light through the front face, i.e., to reduce reflections. However, it has been found that, even with coatings of this kind, the mechanical properties of waveguide front faces, and their resistance to fouling, are usually inadequate.